PASSIVE TRANSPONDER SYSTEM AND PRESSURE WAVE MEASURING DEVICE

Abstract

The invention relates to a passive transponder system comprising a first or second conductor loop structure and a first and a second capacitive pressure sensor, wherein each conductor loop structure is coupled to one of said capacitive pressure sensors to form a resonant circuit, and the first conductor loop structure is positioned at a non-vanishing angle in relation to the second conductor loop structure. The resonant frequencies of the resonant circuits are selected such that they do not overlap to result in beating. The invention also relates to a pressure wave measuring device comprising such a passive transponder system, and a readout unit.

Claims

1-23. (canceled)

24. A passive transponder system comprising a first conductor loop structure having at least one turn, a second conductor loop structure having at least one turn, a first capacitive pressure sensor, a second capacitive pressure sensor, wherein the first capacitive pressure sensor is electrically coupled to the first conductor loop structure to form a first resonant circuit with a first resonant frequency, wherein the second capacitive pressure sensor is electrically coupled to the second conductor loop structure to form a second resonant circuit with a second resonant frequency, wherein the at least one turn of the first conductor loop structure is wound around at least one first turn axis, wherein the at least one turn of the second conductor loop structure is wound around at least one second turn axis, and wherein the at least one first turn axis and the at least one second turn axis are at a non-vanishing angle to one another.

25. The passive transponder system according to claim 24, wherein the first resonant frequency and the second resonant frequency differ from one another at least to such an extent that they do not superpose one another in such a way as to produce a beat.

26. The passive transponder system according to claim 24, wherein the first conductor loop structure and the second conductor loop structure are designed as flat coils which are arranged on surfaces of a carrier structure.

27. The passive transponder system according to claim 26, wherein the carrier structure is shaped as part of a cylinder or as a cylinder or as part of a hose or as part of a tube or as a hose or as a tube.

28. The passive transponder system according to claim 27, wherein the carrier structure has or is a plastic tube.

29. The passive transponder system according to claim 27, wherein the first conductor loop structure is arranged on an inner surface of the carrier structure and the second conductor loop structure is arranged on an outer surface of the carrier structure.

30. The passive transponder system according to claim 24, wherein the first conductor loop structure has a plurality of groups of turns, the groups arranged next to one another in the direction of a main axis, each group comprising at least one turn, wherein each of the turns of the same group of the first conductor loop structure is wound around a common first turn axis, wherein the first turn axes of the different groups are in each case spaced apart from one another by a non-vanishing distance, and wherein the second conductor loop structure has a plurality of groups of turns, the groups arranged next to one another in the direction of the main axis, each group comprising at least one turn, wherein each of the turns of the same group of the second conductor loop structure is wound around a common second turn axis, wherein the second turn axes of the different groups are spaced apart from one another by a non-vanishing distance.

31. The passive transponder system according to claim 30, wherein the first turn axis and/or the second turn axes are parallel to one another.

32. The passive transponder system according to claim 31, wherein the turns of the first conductor loop structure extend in two surfaces located opposite one another in relation to the main axis, the first turn axes being perpendicular to said surfaces, and wherein the turns of the second conductor loop structure extend in two surfaces located opposite one another in relation to the main axis, the second turn axes being perpendicular to said surfaces.

33. The passive transponder system according to claim 32, wherein the first turn axes are located between the second turn axes in the direction along the main axis.

34. The passive transponder system according to claim 32, wherein the capacitive pressure sensors are located with their pressure-measuring surfaces in each case in one of the opposing surfaces in which the conductor loop structure of the corresponding resonant circuit extends.

35. The passive transponder system according to claim 34, wherein the resonant frequency of the first and of the second resonant circuit differ by at least twice the bandwidth of that one of the first or second resonant circuit that has the greater bandwidth.

36. The passive transponder system according to claim 24, wherein the first conductor loop structure is formed from a single wire and/or wherein the second conductor loop structure is formed from a single wire.

37. The passive transponder system according to claim 24, wherein the first resonant frequency and/or the second resonant frequency is greater than or equal to 5 MHz, and/or less than or equal to 40 MHz.

38. The passive transponder system according to claim 24, wherein the first and the second conductor loop structure form a vessel support for a blood vessel or a stent.

39. The passive transponder system according to claim 24, wherein the first and/or the second conductor loop structure is made of DFT wire having a core comprising silver or gold and having a sheath comprising NiTi.

40. A pressure wave measuring device comprising a passive transponder system according to claim 24, and a reader unit, wherein the reader unit has a reader coil which can be arranged relative to the passive transponder system in such a way that a magnetic field generated by said reader coil passes through at least one of the conductor loop structures of the transponder system, further comprising evaluation electronics, by means of which a signal that excites the resonant circuits can be applied to the reader coil and a signal received from the reader coil can be evaluated.

41. The pressure wave measuring device according to claim 40, comprising a signal source, by means of which a signal can be generated with the resonant frequencies of the resonant circuits, and further comprising a directional coupler, to the output of which the signal source is electrically coupled and to the input of which the reader coil is coupled.

42. The pressure wave measuring device according to claim 40, further comprising a first mixer and a first low-pass filter arranged behind it, wherein a signal with the first resonant frequency that is received by the reader coil from the transponder system can be downmixed by means of the first mixer, and further comprising a further mixer and a second low-pass filter arranged behind it, wherein a signal with the second resonant frequency that is received by the reader coil from the transponder system can be downmixed by means of the further mixer.

43. The pressure wave measuring device according to claim 40, wherein the pressure wave measuring device is designed to constructively add the signal output from the first low-pass filter to the signal output from the second low-pass filter.

44. The pressure wave measuring device according to claim 41, wherein the pressure wave measuring device is configured to separate the signal generated by the first low-pass filter into amplitude and phase and to separate the signal output from the second low-pass filter into amplitude and phase, and is further designed to add the amplitude separated from the signal generated by the first low-pass filter to the amplitude separated from the signal generated by the second low-pass filter.

45. A method for producing a passive transponder system according to claim 24, wherein the first and/or the second conductor loop structure are produced by stringing a plurality of carrier elements onto a rod, wherein each carrier element has a cylindrical outer surface, in which a cutout shaped as part of a cylindrical surface is formed, wherein the carrier elements are strung onto the rod such that cylinder axes of their cylindrical outer surface are perpendicular to a longitudinal direction of the rod and such that in each case one of the carrier elements is located in the cut-out shaped as part of a cylindrical surface of an adjacent carrier element, wherein then a first wire is wound as a first conductor loop structure around a first group of carrier elements, the cylinder axes of the cylindrical outer surfaces of which are parallel to one another, and a second wire is wound as a second conductor loop structure around a second group of carrier elements, the cylinder axes of the cylindrical outer surfaces of which are parallel to one another.

46. The method according to claim 45, wherein the first and the second wire are each wound in such a way that they run fully around the carrier elements of the relevant group at least once and then run to the respectively adjacent carrier element of the same group.

Description

[0055] In the figures:

[0056] FIG. 1 shows a measuring arrangement for determining a directional characteristic of a transponder,

[0057] FIG. 2 shows a directional characteristic of a transponder comprising two coils,

[0058] FIG. 3 shows a printed circuit for producing an exemplary transponder system according to the invention,

[0059] FIG. 4 shows a side view of this transponder system according to the invention,

[0060] FIG. 5 shows an axial view of this transponder system according to the invention,

[0061] FIG. 6 shows a further example of a transponder system according to the invention,

[0062] FIG. 7 shows a perspective view of the transponder system shown in FIG. 6,

[0063] FIG. 8 shows a detail view of the transponder system shown in FIGS. 6 and 7,

[0064] FIG. 9 shows an axial view of the transponder system according to the invention shown in FIGS. 6 to 8,

[0065] FIG. 10 shows an example of a pressure wave measuring device according to the invention,

[0066] FIG. 11 shows an exemplary connection of two resonant circuits tuned to the same frequency,

[0067] FIG. 12 shows the resonance shift of the resonant circuits shown in FIG. 11, and

[0068] FIG. 13 shows an example of a production method according to the invention.

[0069] FIG. 1 shows a measuring arrangement for measuring the directional characteristic of a transponder 1. The transponder 1 is arranged here with a variable orientation relative to a reader coil 2. The measuring device has an optional angle scale 3, by which the orientation of the transponder can be measured. Here, the reader coil 2 is a cylindrical coil, which can be seen from the side in FIG. 1. The transponder 1 is arranged relative to the reader coil 2 in such a way that an axis of symmetry 4 of the reader coil 2 intersects a cylinder axis of the transponder 1, the axis of symmetry 4 being perpendicular both to the reader coil 2 and to the cylinder axis of the transponder 1. Here, the transponder 1 has saddle-shaped coils which are arranged on cylindrical surfaces of the transponder 1, namely in such a way that the coil axes are perpendicular to the longitudinal axis of the transponder 1 and intersect the axis of symmetry 4 or are coaxial to the latter. The coil axes additionally intersect the cylinder axis of the transponder 1, here the axis of rotation.

[0070] FIG. 2 shows a directional characteristic as measured for a transponder by means of the measuring arrangement shown in FIG. 1 when the transponder 2 has cylindrical coils, the coil axes of which are perpendicular to one another and intersect one another. FIG. 2 shows the X component of the voltage induced in the reader coil and the Y component of the voltage induced in the reader coil, wherein the coil axis of one coil of the transponder runs in the X direction and the coil axis of the other coil of the transponder runs in the Y direction.

[0071] The dotted line 5 (squares) in FIG. 2 shows the directional characteristic of that coil of the transponder which has a coil axis oriented in the Y direction. The line 6 shown in small dashes (spots) shows the directional characteristic of that coil of the transponder which has a coil axis oriented in the X direction. It can be seen that the two individual coils of the transponder 1 have a pronounced figure-of-eight-shaped directional characteristic, the directional characteristics of the two coils being rotated through 90 relative to one another since the coils are also rotated through 90 relative to one another. If the two coils of the transponder 1 are simply connected in series, then the directional characteristic 7 shown in large dashes (triangles) is obtained, which is likewise figure-of-eight-shaped and is rotated through 45 relative to the directional characteristics of the two individual coils. The solid line (circles) shows the directional characteristic of a transponder according to the present invention. Since the signals of the two individual coils differ from one another due to their different resonant frequencies, the signals of the two coils can be constructively added to one another. This results in the directional characteristic denoted 8, which is almost circular. The direction in which reading takes place in the XY plane is of no importance here. A good coupling between the transponder and the reader coil is always achieved.

[0072] FIGS. 3 to 5 show a first example of a passive transponder according to the invention. FIG. 3 shows a printed circuit, from which the transponder can be produced, FIG. 4 shows two side views of the transponder thus produced, and FIG. 5 shows an axial view of the transponder thus produced.

[0073] FIG. 3 shows a printed circuit 33 comprising a first conductor loop structure 31 and a second conductor loop structure. The conductor loop structure 31 is applied to a front side of a substrate 34, facing towards the observer in FIG. 3, and the second conductor loop structure is applied to a rear side of the substrate 34, facing away from the observer. The substrate 34 thus electrically insulates the first conductor loop structure 31 and the second conductor loop structure 32 from one another.

[0074] In the example shown, the conductor loop structures 31 and 32 each have three turns. Each of the conductor loop structures 31 and 32 has two straight regions, which are parallel to one another and are connected to one another via two circularly curved regions. In the straight regions the conductor tracks run parallel to one another and in a straight line, and in the circularly curved regions the conductor tracks run along a circular line and parallel to one another for all turns of the same conductor loop structure. A first capacitive pressure sensor 35 is coupled to the first conductor loop structure 31. The capacitive pressure sensor 35 is coupled between the two ends of the conductor loop structure 31. Correspondingly, the conductor loop structure 32 has a second capacitive pressure sensor 36, which is once again arranged between the two ends of the conductor loop structure 32. The first capacitive pressure sensor 35 together with the first conductor loop structure 31 forms a first resonant circuit with a first resonant frequency. The second capacitive pressure sensor 36 together with the second conductor loop structure 32 forms a second resonant circuit with a second resonant frequency.

[0075] The first conductor loop structure 31 is wound around a turn axis, the turn axis here passing through the centre point of the conductor tracks of the conductor loop structure 31 and being perpendicular to the substrate 34. Correspondingly, the conductor tracks of the second conductor loop structure 32 are wound around a second coil axis, which once again runs through the centre point of the conductor tracks of the second conductor loop structure 32 and is perpendicular to the substrate 34.

[0076] From the structure shown in FIG. 3, it is possible to produce a passive transponder according to the invention as shown in FIG. 4 by bending the substrate 34 about an axis which runs parallel to the longitudinal sides of the substrate 34, which are parallel to the straight sections of the conductor loop structures 31 and 32. This direction will be referred to below as the Z direction.

[0077] FIG. 4A shows this embodiment of the transponder in a first direction which is perpendicular to the Z direction and at an angle of 45 to the X axis and to the Y axis. Sub-FIG. 4B shows the transponder as seen in the direction of the X axis.

[0078] The conductor loop structures 31 and 32 may advantageously be dimensioned such that, when the substrate 34 is bent in the described manner, the straight regions of the conductor loop structures are located precisely diametrically opposite one another in relation to the axis about which the substrate 34 has been bent. The substrate 34 is preferably bent in a circular shape so that the coil axes of the first conductor loop structure and of the second conductor loop structure 32 are at the desired angle to one another, preferably perpendicular to one another.

[0079] FIG. 5 shows the embodiment of the transponder according to the invention which is shown in FIG. 4, as viewed in the direction of the Z axis. The view shown in FIG. 4A is obtained when looking at the view shown in FIG. 5 from the right, and the view shown in FIG. 4B is obtained when looking at it from the top left-hand corner.

[0080] It can be seen that the substrate has been bent into a circular shape. The first conductor loop structure 31 is located on an inner surface of the resulting cylindrical substrate, and the second conductor loop structure 32 is located on the outer surface thereof. The longitudinal regions 31a, 31b and 31c of the first conductor loop structure 31 are located one another, in relation to which the straight sections 31a, 31b, 31c of the same turn of the first conductor loop structure 31 are at the same distance. Correspondingly, the straight sections 32a, 32b, 32c are located opposite one another in relation to the YZ plane, the straight sections 32a, 32b, 32c of the same turn being at the same distance therefrom.

[0081] FIGS. 6 to 9 show a further example of a passive transponder according to the invention. FIG. 6 shows a side view in the direction perpendicular to the Z axis, which corresponds to the longitudinal axis or main axis of the transponder, FIG. 7 shows a perspective view, and FIG. 8 shows a detail view. FIG. 9 shows a view in the direction of the Z axis.

[0082] In this embodiment of the invention, a first wire 61 is bent to form a first conductor loop structure 61 and a second wire 62 is bent to form a second conductor loop structure 62. The first conductor loop structure 61 has a plurality of turns 61a, 61b, 61c arranged next to one another in the direction of a main axis, which here is the longitudinal axis, that is to say the Z direction of the transponder, each of the turns of the first conductor loop structure 61 being wound around a separate turn axis. The first turn axes are parallel to one another and are spaced apart from one another by a non-vanishing distance. The illustrated embodiment additionally has a second conductor loop structure 62 with a plurality of turns 62a, 62b, 62c arranged next to one another in a direction of the main axis, each of the turns 62a, 62b, 62c of the second conductor loop structure 62 once again being wound around a separate second turn axis. The second turn axes are once again parallel to one another and are spaced apart from one another by a non-vanishing distance. In the illustrated example, the turn axes of the first turns 61a, 61b, 61c are additionally perpendicular to the turn axes of the second turns 62a, 62b, 62c. In the illustrated example, the conductor loop structure 61 additionally has, on each of the turn axes, two turns which are located opposite one another in relation to the Z axis. In addition, the second conductor loop structure 62 also has, for each of the turn axes, two turns located opposite one another in relation to the Z axis.

[0083] As can be seen in the detail in FIG. 8, the turns 61a, 61b, 61c of the first conductor loop structure 61 are interwoven with the turns 62a, 62b of the second conductor loop structure 62. To this end, the wire of the first conductor loop structure 61 is firstly bent to form a substantially circular turn, the turn being closed as a result of the wire being wound around the wire of the second conductor loop structure 62, where it runs between two turns 62a and 62b of the second conductor loop structure. Correspondingly, the wire of the second conductor loop structure 62 is bent to form a turn 62a which is closed as a result of the wire being wound around the wire of the first conductor loop structure 61, where it runs between two adjacent turns 61a and 61b of the first conductor loop structure. In this way, for each of the conductor loop structures 61 and 62, in each case the wire is bent to form a turn, then is guided along a straight region parallel to the cylinder axis of the transponder to the adjacent turn of the same conductor loop structure, is bent there once again into a turn and is guided onwards in a straight region to the adjacent turn of the same conductor loop structure, this being repeated for the number of turns in the same surface of the relevant conductor loop structure. The second conductor loop structure is correspondingly wound to form turns 62a, 62b, which are once again guided over straight regions parallel to the longitudinal axis of the transponder. The turns of the second conductor loop structure 62 are in each case wound in a sub-region of the turns around the straight region of the first conductor loop structure 61. Correspondingly, the turns 61a, 61b, 61c of the first conductor loop structure 61 are wound in the region of the turn around the straight region of the adjacent second conductor loop structure.

[0084] It should be pointed out that the form of winding shown here is merely one advantageous example that results in good mechanical stability. However, many other types of winding are conceivable which lead to an identical arrangement of the turns of the conductor loop structures 61 and 62. It is also possible that the conductors of the conductor loop structures 61 and 62 are connected to one another in some other way, for example by adhesive bonding or by being bound together.

[0085] FIG. 9 shows a view of the example of the transponder according to the invention shown in FIGS. 6 to 8, as seen in the direction of the longitudinal axis of the transponder, that is to say in the direction of the Z axis. It can be seen that the conductor loop structures 61 and 62 describe an approximately circular circumference, so that the transponder as a whole describes approximately a cylinder shape.

[0086] Here, too, the first conductor loop structure 62 is coupled at its ends to a first capacitive pressure sensor 63, and the second conductor loop structure 62 is coupled to a second capacitive pressure sensor 64.

[0087] FIG. 10 shows an exemplary circuit diagram of an inventive pressure wave measuring device according to the invention. The pressure wave measuring device according to the invention comprises a passive transponder as described above, which is illustrated here by a first resonant circuit 101 and a second resonant circuit 102. The first resonant circuit 101 has a first capacitive pressure sensor 103 and the second resonant circuit 2 has a second capacitive pressure sensor 104, which are shown as capacitances in FIG. 10. In addition, the first resonant circuit 101 has a first conductor loop structure 105 and the second resonant circuit has a second conductor loop structure 107.

[0088] The measuring device shown in FIG. 10 additionally comprises a reader unit 108, by means of which the resonant circuits 101 and 102 can be read. The reader unit 108 has a reader coil 2. By means of a signal source 109, it is possible to generate a signal, that is to say a current signal, with two superposed frequencies .sub.a and .sub.b, wherein the component with the frequency .sub.a is generated with an amplitude a and the component with the frequency .sub.b is generated with an amplitude b. The signal form a.Math.sin(.sub.at)+b.Math.sin(wbt) is thus obtained. The signal thus generated is fed via a directional coupler 110 into the reader coil 2. The directional coupler is coupled to a first mixer 111 and to a second mixer 112, into which a signal received by the directional coupler 110 from the reader coil 2 can be fed. The signal obtained from the reader coil is mixed with the reference signal a.Math.sin(.sub.at) in the first mixer 111 and with the reference signal b.Math.sin(.sub.bt) in the second mixer 112.

[0089] The signal output from the first mixer 111 is then fed to a low-pass filter 113. The signal output from the second mixer 112 is fed to a low-pass filter 114. The first low-pass filter 113 is then split by the reader unit 108 into an absolute value or an amplitude 115 and a phase 116. The signal output from the second low-pass filter 114 is likewise split into an amplitude 117 and a phase 118. The absolute values 115 and 117 of the first and second signal are added by means of an addition 119 in order to obtain a sum 121. The phases 116 and 118 of the first and second signal are added by means of a further adder 120 in order to obtain a sum 122. The signal 121 and 122 thus obtained then has a circular directional characteristic, as shown by the solid line (circles) in FIG. 2.

[0090] It should be pointed out that the mixers 111, 112 and the low-pass filters 113, 114 serve to improve the signal. They are therefore optional.

[0091] FIG. 11 shows a circuit in which two resonant circuits 1101 and 1102 set to the same frequency are coupled to one another via two coils L1 and L2 with a coupling factor K1. The interaction thereof is illustrated as a function of K1. The greater K1, the greater the interaction between the coils C1 and C2 and the greater a resulting detuning. Besides the coil L1, which in the illustrated example has an inductance of 3, the first resonant circuit has a capacitance C1 of 10 pF and a resistance R1 having a value of 0.1. The second resonant circuit 1102 comprises the second coil C2, a second capacitance C2 and a second resistance R2 having the same values as in the first resonant circuit 1101, so that the two resonant circuits 1101 and 1102 have the same resonant frequency. A voltage V1 is applied to the first resonant circuit 1101, by means of which the latter can be made to oscillate.

[0092] FIG. 12 shows the impedance UIN/IIn, measured in the first resonant circuit, as a function of the frequency f/f.sub.0 for different coupling factors K1. The value f.sub.0 is the resonant frequency of the two resonant circuits 1101 and 1102 in the uncoupled state. The various curves show different values of the coupling factor K1. It can be seen that there is no shift in the resonant frequency with a very small coupling of K1=0.001 (solid line). If the coupling is increased, however, it can be seen that the resonant frequencies of the two resonant circuits diverge.

[0093] FIG. 13 shows an exemplary production method for producing a passive transponder according to the invention. In a first step, a plurality of carrier elements 132 are strung onto a rod 131. Each carrier element 132 has a cylindrical outer surface, in which a cutout 133 shaped as part of a cylindrical surface is formed. The carrier elements 132 are strung onto the rod in such a way that the cylinder axes of their cylindrical outer surfaces are perpendicular to a longitudinal direction of the rod 131, and in such a way that additionally in each case one of the carrier elements 132 is located in the cutout 133 shaped as part of a cylindrical surface of an adjacent carrier element 132. This state can be seen in FIG. 13B.

[0094] Carrier structures can also be produced as shown in FIGS. 13C and 13D, wherein the variant produced in 13D can be obtained from the method shown in sub-figures A and B.

[0095] Then, as illustrated in dotted line in FIG. 3B, a first wire as the first conductor loop structure and a second wire 135 as the second conductor loop structure 135 are wound around the carrier elements 132. The winding may take place in such a way as to result, for example, in a structure as shown in FIGS. 6 to 9. On completion of winding, the elements 132 can be removed so that only the conductor loop structures remain. To this end, the rod 131 shown in FIGS. 13A and 13B for example can be removed. Preferably, the wires 134 and 135 are each wound around each of the carrier elements 132 at least once, so that one turn is obtained in each case.